Carbon dioxide exchange and the mechanism of environmental control in a farmland ecosystem in North China Plain
- Publication Type:
- Journal Article
- Science in China, Series D: Earth Sciences, 2006, 49 (SUPPL. 2), pp. 226 - 240
- Issue Date:
CO2flux was measured continuously in a wheat and maize rotation system of North China Plain using the eddy covariance technique to study the characteristic of CO2exchange and its response to key environmental factors. The results show that nighttime net ecosystem exchange (NEE) varied exponentially with soil temperature. The temperature sensitivities of the ecosystem (Q10) were 2.94 and 2.49 in years 2002-2003 and 2003-2004, respectively. The response of gross primary productivity (GPP) to photosynthetically active radiation (PAR) in the crop field can be expressed by a rectangular hyperbolic function. Average Amaxand α for maize were more than those for wheat. The values of α increased positively with leaf area index (LAI) of wheat. Diurnal variations of NEE were significant from March to May and from July to September, but not remarkable in other months. NEE, GPP and ecosystem respiration (Rec) showed significantly seasonal variations in the crop field. The highest mean daily CO2uptake rate was -10.20 and -12.50 gC·m-2·d-1in 2003 and 2004, for the maize field, respectively, and -8.19 and -9.50 gC·m-2·d-1in 2003 and 2004 for the wheat field, respectively. The maximal CO2uptake appeared in April or May for wheat and mid-August for maize. During the main growing seasons of winter wheat and summer maize, NEE was controlled by GPP which was chiefly influenced by PAR and LAI. Recreached its annual maximum in July when Recand GPP contributed to NEE equally. NEE was dominated by Recin other months and temperature became a key factor controlling NEE. Total NEE for the wheat field was -77.6 and -152.2 gC·m-2·a-1in years 2002-2003 and 2003-2004, respectively, and -120.1 and -165.6 gC·m-2·a-1in 2003 and 2004 for the maize field, respectively. The cropland of North China Plain was a carbon sink, with annual -197.6 and -317.9 gC·m-2·a-1in years 2002-2003 and 2003-2004, respectively. After considering the carbon in grains, the cropland became a carbon source, which was 340. 5 and 107. 5 gC·m-2·a-1in years 2002-2003 and 2003-2004, respectively. Affected by climate and filed managements, inter-annual carbon exchange varied largely in the wheat and maize rotation system of North China Plain. © Science in China Press 2006.
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